The present invention relates to the technical field of water abrasive suspension blasting (WASB) and here particularly to the bypass principle for producing WASB. Water abrasive suspension blasting is used for example in degrading technology below and above water. With this for example projectile casings are degraded in order to be able to remove and dispose of explosive substances located therein whilst avoiding flying sparks. The water abrasive suspension blasting has also shown to be successful with the degrading of atomic power stations, in particular on degrading the pressure container. Further fields of application are offshore technology, as well as in the field of petrochemical industry when it is the case of separation in an environment endangered by explosion.
The devices functioning according to the bypass principle consist essentially of a high-pressure pump which conveys water as a carrier fluid into a main conduit with a throttle member, and parallel into a secondary conduit (bypass). The secondary conduit opens out into a pressure container in which the abrasive medium is located, wherein the fluid flow led in the secondary conduit goes through the pressure container, entrains abrasive medium here and via a conduit out of the pressure container is again supplied to the main conduit. This suspension is delivered via a dispensing nozzle which via a flexible conduit may be arranged where necessary several hundred metres away from the device.
Whilst the carrier fluid is available from a supply container or the water supply network mostly in an adequate quantity over a longer time for the continuous operation of the device, the quantity of abrasive medium which is available is dependent on the size of the pressure container. If the abrasive medium located in the pressure container is used up the pressure container must be filled and the water abrasive suspension blasting must be interrupted during this time.
Although there are known devices which alternately operate with two pressure containers so that a continuous operation is possible, the expense with regard to apparatus is very great. Furthermore pressure fluctuations occur during the change or switch-over of the pressure container so that also here a continuous operation is not possible.
From EP 0 276 219 B1 there is known a device of the known type with which there is provided only one pressure container in which before being filled the high-pressure pump is switched off and thus the suspension jet is interrupted. For filling there is provided a circulatory path in which the abrasive medium together with fluid from a supply container is pumped into the pressure container and from here again into the supply container. At the same time the leading of the conduit through the pressure container is designed such that the abrasive medium settles in this, whereas the fluid is led running back into the supply container. The construction of the circulatory path decoupled from the main flow for filling the pressure container, is likewise expensive with regard to apparatus. The fittings provided within the circulatory path must with regard to design be formed such that they are not compromised in their function by the abrasive medium which compellingly settles here.